Polyepoxide foam



United States Patent Ofiice 3,373,121 Patented Mar. 12, 1938 Theinvention relates to an improved resinous solid cellular foam. It moreparticularly relates to the porous cross-linked reaction product of adiglycidyl compound and a polyalcohol.

Solid cellular foams are known. They compose a large class of materialswidely used for cushioning and insulating and for the construction ofarticles, panels, and furnishings in general. The suitability of a foamfor a particular use is largely dependent on such properties as tearresistance, flexibility, resiliency, resistance to oxidative effects,and its cell structure, e.g., whether it is of closed structure or ofconnecting or open cell structure.

The invention provides a foam which meets this need. The manufacturethereof does not require highly specialized equipment and does not usehazardous or obnoxious materials. It is resilient, possesses good tearresistance, and is durable, has low thermal and electrical conductiveproperties, and is long lived in use in the presence of oxygen andmoisture.

The foam of the invention consists essentially of the reaction productof: (A) and (B), in the presence of (C) and (D) below, where:

(A) is a diglycidyl compound selected from the class consisting of:

O 12 CRC CH2 wherein R is a substituent selected from the classconsisting of H, CH and (3 1-1 and R is selected from the class havingthe formula:

The general procedure followed in making a foam is to cause a gas to beeither generated in situ or to be introduced into a rubber or resinousmaterial in a liquid but curable state. The gas may be generated in situeither by chemical reaction or by application of heat. When introduced,it is usually admitted under pressure through a plurality of relativelysmall apertures into a confined mass of the resinous or rubber liquid.The rate of generation or introduction of the gas is controlled so thatat least a portion of the gas is at least temporarily trapped in theexpanding curing mass. Materials presently employed in making foaminclude polymeric materials of high molecular weight such as natural andsynthetic rubber and polystyrene and polymerizable systems such asdiisocyanate polyglycol mixtures.

Many known resinous solid foams are not fully satisfactory. For example:if they are suficiently tough, they are often too rigid; if they aresufficiently resilient, they often become more-or-less permanently setor compressed after a period of continuous load bearing; if they aresubjected to prolonged contact with air, particularly in the presence oflight, they often become tacky or softened, or become brittle and evencrumble away in a gradual disintegrating process.

Efforts have been made to provide a solid foam which overcomes some ofthe above disadvantages by employing a diglycidyl ether, e.g., admixinga diglycidyl ether of a bisphenol with the reaction product of apolyamide resin and N,N'-dinitroso-N,N'-dimethyl terephthalamide,wherein nitrogen gas is liberated in situ as in US. Patent 2,936,294 oradmixing a liquid or solid readily convertible to a gas by heat, with adiglycidyl ether of a hisphenol, heating said mixture for a prescribedtime and then admixing therewith an amine type curing agent, and heatingan additional period as in US. Patent 2,739,134. Foams .of this naturehave limited utility and do not have the desirable properties for anumber of uses requiring solid foam.

A need exists for a cellular solid foam which is conveniently preparedand which possesses a composite of properties such as increasedtoughness, unimpaired re siliency over a wide range of temperatures,uniformity of cell structure, especially good chemical resistance andelectrical properties, and long life in service under condi tions ofcontinued stress and subjection to the degenerative effects of air andlight.

wherein R has the same significance as above; and n is from 0 to 10;

(b) tcHn wherein m is from 4 to 18; and

generally. The term, polyalcohol, means an aliphatic alcohol having anhydroxyl functionality of about two or more, i.e., itincludes'difunctional, trifunctional, and higher alcohols. Illustrativeof polyalcohols are the glycols, glycerol, pentaerythritol, mono-ethersof pentaerythritol and of glycerol, and glycerol and glycols withhydroxy-alkoxyalkoxy substitution on carbon. The hydroxyl groups of thepolyalcohol may be primary or secondary but may not be tertiary.

The term, diglycidyl compound, as used herein, includes those havingsomewhat less than two oxirane groups per molecule, e.g., those havingan average of from 1.6 to 2 oxirane groups per molecule.

When the polyalcohol employed has an average hydroxyl functionality ofmore than two, the amount of the diglycidyl compound to employ need notbe greater than that necessary to provide an equivalent number ofoxirane groups per equivalent number of hydroxyl groups in thepolyalcohol to obtain a relatively low density foam. On the other hand,when the polyalcohol employed is a diol, the amount of the diglycidylcompound to employ to obtain a relatively light density foam is greaterthan that necessary to provide an equivalent number of oxirane groupsper equivalent number of hydroxyl groups in the polyalcohol.

3 The reaction thought to take place when a diglycidyl compound and adiol are reacted in amounts which provide an excess of oxirane groupsover hydroxyl groups in the diol may be represented as follows:

' first of the two steps may be stored for long periods of time andconverted to a foam at a convenient later date. It also provides bettercontrol over the density of the foam being made. a

For the purposes of ascertaining suitable proportions of the diglycidylcompound and a suitable polyalcohol to employ, an unblown sample mixturemay be made by admixing the selected diglycidyl compound and polyalcoholwith about 2 to percent by weight of a suitable Friedel- Craftscatalyst, e.g., a 48% solution of BB, in diethyl ether, in the absenceof a blowing agent. If a tough prodnot is obtained within about 3minutes, the proportions employed are satisfactory for use in making thefoam of the invention. The recommended amounts of the diglycidylcompound and polyalcohol to employ are those sufficient to provide aratio of bet-ween about 1.5 and 3.0 equivalents of oxirane groups perhydroxyl group of the polyalcohol, a ratio of between about 2.0 and 2.5oxirane groups to one hydroxyl group usually being provided.lllustrative of a standard mixture to employ for comparative purposes isone consisting of an admixture of 110 millimole equivalents of aproduct, having the structure below and the average compositioncorresponding to n=12.6:

. CH2CHCHzOL-CHCH2O I 14 millimoles of glycerine, and millimoles of aproduct, having the structure below and the average compositioncorresponding to n=34,:

CH3 '1 HO- H-CH LC POI-In The catalyst to employ in the practice of theinvention may be any Friedel-Crafts or Lewis acid type catalyst, e.g.,BF SnCl SbCl AlCl and amine and ether complexes thereof.

Blowing agents which may be employed are any substantially chemicallyinert liquid or solid which can be completely readily dispersed in thereaction mixture and which is readily converted to a gas at acontrollable rate upon the application of heat. It is recommended thatthe blowing agents have a boiling point of less than about 100 C. andpreferably below 60 C. Examples of suitable blowing agents are theFreons, low boiling hydrocarbons such as butane and pentane, andhalogen-substituted derivatives of hydrocarbons.

The preferred blowing agent to employ is a chlorofluoro ethane, e.g.,CClF -CCIF and CF Cl-CFCl or chlorofluoro methane, e.g., CFCl having aboiling point between 0 C. and 60 C., or a mixture boiling in thisrange.

The amount of the catalyst to employ is between 1 and 5 percent byweight of the diglycidyl compound and polyalcohol reaction mixture. Theblowing agent is usually added as a liquid and accordingly is employedat a temperature below the boiling point thereof. The reaction betweenthe diglycidyl compound and polyalcohol is exothermic and the blowingagent is readily volatilized, producing cellular voids in the reactionmixture and converting it into an intumescent structure simultaneouslyas the cure proceeds. A few drops of an unreactive liquid which isincompatible with the reaction mixture, e.g., a silicone, is usuallyadmixed therewith prior to admixture of the Friedel-Crafts catalyst toprovide an open cell structure among such unreactive silicones arepolymers of dimethyl siloxanes. When used, they are usually employed inthe amount of between about 0.1% and 5.0%, by weight, of thecomposition.

The invention may be practiced by one of two modes of procedure. Onemode is a one-step procedure which consists of admixing the polyalcoholand diglycidyl compound together and admixing therewith a Friedel-Craftsor Lewis type acid and a blowing agent.

The preferred mode of practicing the carry it out in two steps, asfollows:

Step 1.Admix (1) a diglycidyl ether of a polyalcohol or mixture of suchethers (2) a polyalcohol, e.g., polyoxypropylene glycol, in amounts soas to provide a stoichiometric excess of the polyalcohol and (3) a smallamount of a Friedel-Crafts catalyst or complex thereof, e.g., BF :(C HO, in a reaction vessel equipped with a stirrer, heat-control means andthermometer or thermoinvention is to couple. The mixture so made may bewarmed to initiate reaction, if necessary, to between about 40 and 50 C.and thereafter controlled at a temperature between about 60 and 70 C.until the reaction has progressed sufficiently for it to have aviscosity of between about 4,000 and 20,000 centipoises.

Step 2.The reaction mixture of Step 1 (usually after cooling to betweenabout 20 and 40 C.) is admixed with more of a diglycidyl compound toprovide the desired excess thereof, a Friedel-Crafts catalyst, e.g.,additional BF :'(C H O, usually between about 1 and 5 weight percentbased on the weight of the reaction mixture, and a blowing agent, e.g.,between about 10 and 30 percent of a Freon. Usually between about 1% and5% of a silicone is admixed therewith to promote an open cell structure.The mixture reacts and simultaneously expands into a cellular solid foamhaving a density of between about 1 and 10 pounds per cubic foot.

, In practicing the invention, it is often advantageous to employ as lowa ratio of the more expensive diglycidyl ether to the less expensivepolyalcohol as will yield a satisfactory foam. To attain this objective,a high molecular weight polyalcohol is usually employed. One of suchalcohols which is highly satisfactory is the condensation productobtained by reacting propylene oxide with glycerol; A triol is thusproduced which usually has a molecular weight of between about 2,000 and5,000 and preferably not over about 3,500, e.g., 3,000. Accordingly,although a molar excess of the diglycidyl compound is employed with thepolyol, the ratio by weight of the polyalcohol is greatly in excess ofthat of the diglycidyl ether.

A further modification of the practice of the invention is to employ asthe polyalcohol a mixture of polyoxypropylene glycol, having arelatively high molecular weight of between about 1,000 and 2,500, e.g.,about 2,000, and one having a relatively low molecular weight such asglycerol, in an amount sufficient to provide between about 5 and 10percent by weight of the resulting glycerol-polyoxypropylene glycolmixture. The objective of employing a preponderance by weight of thepolyalcohol over the diglycidyl compound and yet provide a molar excessof oxirane groups is, therefore, attained similarly to employing thecondensation product of an alkylene oxide and glycerol as explainedabove. The preferred polyalcohol recommended is one having 3 or morehydroxyl groups per molecule and one having an hydroxyl equivalentweight of between about 500 and about 1000'. (By hydroxyl equivalentweight is meant the weight of the polyalcohol necessary to provide oneequivalent weight of hydroxyl groups.) It is also recommended that, whenthe polyalcohol employed has a carbon-to-oxygen ratio of less than 3,the diglycidyl ether employed be water-insoluble and be used in anamount sufiicient to provide at least about 50% by wei ht of thecomposition. Un-

6 Dow Corning silicone No. 200 (which had a viscosity of aboutcentistokes) is illustrative, about 0.5 milliliter of BF :(C H O, and4.3 grams of 1,1,2 -trichloro- 1,2,2- trifiuoro ethane, a high-boilingFreon. A fine-textured less such diglycidyl ether is used in suchamount, the re- 5 open cell foam was formed.

sulting foamed product may be undesirably water-sensitive. On the otherhand, when such diglycidyl ether is EXAMPLE 5 thus used in apreponderant proportion, diethylene glycol Step P 4 was repFifted exceptthat the may be employed as the polyalcohol in the practice of thePolymer was Prepared Y admlxlng 3200 grfims of Poly invention to producea Satisfactory foam. 1O oxypropylene glycol, having a molecular weightof 2000,

The f ll i examples are set out f purposes f 1- and 557 grams of thedlglyc dyl ether mixture employed lustrating the practice or" theinvention but are not to be above, and thfireafier admlxmg addltlQnal2000 of construed as limiting, the scope of the invention being the P YYP PY glycol havmg Previously q x that described hereiirbefore and asdefined in the ap therewith 5 milliliters of li 2: 5)2 The resultingpended claims. 15 mixture was heated to 75 C. which thereafter, due toEXAMPLES 1 3 exothermic heat, rose to 85 C. and was then cooled to J theambient temperature. Titration showed that over 90% These examplesillustrate the one-step procedure af ore of the oxirane groups presenthad reacted described. The selected p olyalcohol, diglycidyl ether,Frie- Step mixture of 1526 grams of the prepolymer i' catalyst f m iWEI-e ff a so formed, 3.3 grams of the diglycidyl ether employed smtablevessel Wlth mlxmg Coohng above, and 2 drops of Dow Corning silicone No.200 (visand tempsrature'mcordmg i The i i cosity of 50 centistokes) wasprepared. Freon 113 (10 Found .employed was dlglfcldyl ether QZ Wmilliliters) and 100 drops (about 5 milliliters) of a 4.8% deltadlphenpl' i i employed was a by solution (of a 48% solution of BF indiethyl ether) in Weight Solutlon 3 m dlethyl ether 95 dioxane wereadmixed therewith. Within about seconds The t P i moleculal: i eqhlva'the mixture had foamed into a tough, highly resilient lent ratios 01 thepolyalcohol and diglycldyl ether emfoam having a density of 8 pounds percubic foot ployed, the amount in grams of catalysts employed, and theamount in milliliters of Freon employed, as Well as EXAMPLE 6 thedensity of the resulting foam, are set out in Table I To show the effectof employing other Friedel-Crafts below: 30 catalysts than BF theunblown sample test, set out here- TABLE I Diglycidyl Ether ofMilli-equiv- Isopropylidenediphenol Freon BF Density Example Name AmountMilligram alents of 113 in etherate of foam in No. in grams moleshydroxyl Amount Milligram Milli-equivml. added 1b./cu.ft.

groups in grams moles alents of epoxide 1 Ziiv i %3 hed{ 5 0 5 9.5 28 561.25 lgram 5.5

with glycerol. 1. 25 13. 6 40. 8 2 8:? 2:3 9.5 28 56 2. 09 do-- 5.0 3Teracol 10.0 3.3 6.6 17.4 51.2 102.4 13.0 do 4.0

1 Freon 113 is triehlorotrifiuoroethane, i.e., CCl CF 1 Added as Freon113 encapsulated in beads of polystyrene.

3 A polymerized tetrarnethylene oxide diol (mol wt. of 3,000).

The foam made by each of the examples set out in inbefore was run,employing the polyalcohol and digly- Table I was examined and found tobe highly resistant cidyl ether in the proportions employed in Example 1but, to tear, had good compression and modulus, (i.e., it reinstead ofthe BF :etherate, employing a solution of 10 covered substantially fullyand quickly after compresgrams SbCl dissolved in 40 grams ethyl acetateas the sion) and was highly useful as a cushioning and/ or insucatalyst.This solution was used in the amount of 1 part lating material. SbCl per100 parts of polyalcohol and diglycidyl ether.

EXAMPLE 4 A polymer sheet was cast without blowing agent in order toevaluate the catalyst. The rate of cure and the properg i gg fIllustrates the two'step Procedure Set ties of the polymer sheetprepared employing and Step prepolymer was prepared by admixing in aSbCl were compared and found to be quite similar in suitable vessel 3436grams (1.72 mole) of polyoxypropylproperties EXAMPLE 7 ene glycol havinga molecular weight of 2000 and 554 grams (1.64 mole) of the diglycidylether, employed in Example 6 was repeated except that about 5% of SnClExamples 1 to 3 above, at ambient temperature. This 59 was employed asthe Friedel-Crafts catalyst. The mixture provided a ratio of equivalentWeight of the ether to the gel ed in 3 minutes and subsequently cured toa tough equivalent weight of the polyalcohol of 0.948. About p lym rhaving high tear resis ance of comparable ex- 0.05 percent of BF gas, byWeight of the ea ti mi cellence to the standard reference mixture. ture,was passed thereinto. The temperature rose to between 60" and 70 C. andthen gradually subsided to EXAMPLE 8 ambignt temper-aura Theprepolymelhad a viscosity of This example illustrates the practice ofthe invention about 00 centipoises employing a diglycidyl ether of abisphenol and a poly- Step 75 grams of the prepglym-er so made werealcohol of greater functionality than 2. A triol (made by then admixed0.66 gram (1.94 millimole) of the diglyreactmg glycerol with Propyleneoxfde having a cidyl ether employed in Step 1, 12-14 drops of a polymlecular weight of 3000) was admlXfll Wlth glycerol in of dimethylsiloxane having repeating units of the relative amount of lo parts ofthe triol and 1.25 parts CH CH of glycerol. There was also admixedtherewith about 1 a milliliter of a silicone (Carbide and CarbonSilicone L520) -and s '0 P 0 Ha vto control cell size in the foam',about 0.1 milliliter of a surfactant known as Tween 40 (which is apolyoxyalkylene 7 8 sorbitan monopalmitate obtained fiom the AtlasPowder and 2 vicinal oxirane groups per molecule selected Company) andDER 332 which is the diglycidyl ether of from the class consisting of:4,4-isopropylidenediphenol and having an epoxide equiva- O O lent weightof 179. To the mixture so formed were ad- R mixed a solution consistingof 1 gram of BF -etherate, 5 5 Hr l grams of the above described triol,and 5 grams of Freon 113. Foaming began immediately and was completewithh i R i a b ti t l t d fr th in about seconds. The density of thefoam was 5 class consisting of H, CH and C H andRis pounds/ cu. ft.selected from the class having the formula:

@ i" w oHroG0Q-ooHeCHoHiO-0o-oHt Having described our invention, what weclaim and dewherein R has the same significance as in (l) sire toprotect by Letters Patent is: abo and n i from 0 to 10;

1. A cellular resinous solid foam consisting of the reaction product of:(b) f component (A) a diglycidyl compound selected from 2 2 the classconsisting of: t

(1) O 0 wherein R has the same significance as in (1) R above andp isfrom 1 to 15;

(2) a mixture of the glycidyl compounds of (a) and (b), and wherein R isa substituent selected from the as component B a polyfunctional alcoholselected class consisting of H, CH and C H and R is from the classconsisting of selected from the class having the formula: (1)polyoxyalkylene glycols, having an aver- Q i S t Q Q -CHa--O -oOCH2CHCH2O o OCH2 wherein R has the same significance as in (1) agemolecular weight of between about above and n is from 0 to 10; 1,000 andabout 2,500, (b) (2) reaction products of propylene oxide and glycerolhaving an average molecular TCHFOGCHCHNTMOHP weight of between about2,000 and about wherein R' has the same significance as in (1) 3,500, d

above and p is from 1 to 15; 40 (3) mixtures of the polyoxyalkyleneglycols (2) a mixture of the diglycidyl compounds of (a) f (1) or th tioduct of (2,) or and (b), and 7 both (1) and (2) with glycerol in aweight component (B) a polyfunctional alcohol selected from o o tio fbetwee about 99 and 90 perthe class consisting of (1) polyoxyalkyleneglycols, t of a polyfunctional alcohol selected having an averagemolecular weight of between f (1), (2), and mixture f both (1) about1,000 and about 2,500, (2) reaction products d (2) d b tw bout 1 d abo t10 0f P PY Oxide and glycerol having an average percent of the glycerol,in an amount of molecular weight of between about 2,000 and aboutcomponent (B) sufiicient to provide a 3,500, and mixtures of the p y yystoichiometric excess of hydroxyl groups cols of (l) or the reactionproduct of (2) or of both over th oxirano groups f component (A); andWith glycerol in a weig Proportion of (II) admixing with theintermixture of components between about 99 and 90 percent of the'polyfunction- (A) and (B) a first portion of a Frieda-Cr ft cata- 1alcohol, selected from and and mixtures lyst as component (C) in anamount suflicient to of both and and between about 1 and about initiatebut insuflicient to efiiectuate complete cross- 10 percent of theglycerol to provide a molar ratio of 5 li ki f components (A) and (B);oxirane groups comprising component (A) to hy- (III) r ing the mixtureof (A), (B), and (C), to a droxyl groups comprising c mpon n (B) fbetween temperature of between about 40 C. and about 70 1.5 and 3; C.until the mixture has a viscosity of between about (C) a Frledel-crafiscatalyst to eff cross-l nk g 4,000 and about 20,000 centipoises,measured at a of componentsA and B; standard temperature of about 25 C.;

(D) a blowing agent selected from the class consisting (IV) Cooling themixture of components (A), (B), of substantially chemically inert gasesand inert liquids and (C) to between about 20 C. and about 40 C.; andsolids which yieldasubstantially chemically inert (V) Admixing with theso cooled mixture of comexpanding gas in controlled amounts whendispersed ponents (A), (B), d (C) in the reaction mixture upon theapplication of heat, 5 (1) a final portion of the glycidyl compounds inan amount sufiicient to produce a foamed product comprising component(A) i an amount fii.. 0f deSlIed ycient to provide in toto, a molarratio of oxirane 2. The cellular resinous solid foam of claim 1 whereingroups to the hydroxyl groups of between about the expanding gas isprovided by a liquid, entrapped in 1,5 d 3, s i p yr d which liquidconverts to a gas (2 adding a final portion of said Friedel-Crafts atmoderate increases in temperature. catalyst comprising component (C) inan 3. The method of making foamed resinous composition 7 amount ffi i tt ff t t -li ki f comprising the steps of: components (A) and (B); andpromptly, be-

(I) admixing as component (A) a first portion of a fore cross-linkinghas appreciably progressed,

glycidyl compound having an average of between 1.6 advising 9 (3) ablowing agent selected from the class consisting of substantiallychemically inert gases and liquid and solids yielding inert gases incontrolled amounts, when dispersed in the reaction mixture, upon theapplication of moderate heat, and (VI) subjecting the composition to atemperature of between about 40 and 70 for a time suflicient to convertthe mixture to a fine textured open cell epoxy foamed resin.

4. The cellular resinous solid foam of claim 1 wherein the amounts of(A) and (B) are such as to provide between about 1.5 and 3.0 equivalentsof oxirane groups contained in (A) per equivalent of hydroxyl groupscontained in (B).

5. The cellular-resinous solid foam of claim 1 wherein the diglycidylcompound is a diglycidyl ether of an isoalkylidenediphenol.

6. The cellular resinous solid foam of claim 1 wherein theisoalkylidenediphenol is 4,4'-isopropylidenediphenol.

7. The cellular resinous solid foam of claim 1 wherein theFriedel-Crafts catalyst is employed in an amount between about 1 and 5percent by weight of the composition.

8. The cellular resinous solid foam of claim 7 wherein theFriedel-Crafts catalyst is BF 9. The cellular resinous solid foam ofclaim 1 wherein the expanding gas is selected from the class consistingof 1 0 chlorofluoroethanes containing at least two fluorine atoms permolecule and boiling between 0 and C., trichlorofluoromethane, andmixtures thereof.

10. The cellular resinous solid foam of claim 1 wherein the expandinggas is an inert gas-yielding liquid entrapped in solid polystyrenebeads.

References Cited OTHER REFERENCES Physical Properties, 1957 edition,Carbide and Carbon Chemicals Co.

Rigid Urethane Foams-J1, Chemistry and Formulation Elastomer Chem. Co.

MURRAY TILLMAN, Primary Examiner. LEON I BERCOVITZ, GEO. F. LESMES,Examiners. M. FOELAK, Assistant Examiner.

1. A CELLULAR RESINOUS SOLID FOAM CONSISTING OF THE REACTION PRODUCT OF:COMPONENT (A) A DIGLYCIDYL COMPOUND SELECTED FROM THE CLASS CONSISTINGOF: